CN114805058A - Method and device for recovering lactic acid from polylactic acid synthetic substrate - Google Patents
Method and device for recovering lactic acid from polylactic acid synthetic substrate Download PDFInfo
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- CN114805058A CN114805058A CN202210419951.7A CN202210419951A CN114805058A CN 114805058 A CN114805058 A CN 114805058A CN 202210419951 A CN202210419951 A CN 202210419951A CN 114805058 A CN114805058 A CN 114805058A
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- lactic acid
- polylactic acid
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- synthetic substrate
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- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 title claims abstract description 194
- 235000014655 lactic acid Nutrition 0.000 title claims abstract description 97
- 239000004310 lactic acid Substances 0.000 title claims abstract description 97
- 239000000758 substrate Substances 0.000 title claims abstract description 91
- 229920000747 poly(lactic acid) Polymers 0.000 title claims abstract description 68
- 239000004626 polylactic acid Substances 0.000 title claims abstract description 68
- 238000000034 method Methods 0.000 title claims abstract description 40
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 65
- 230000010355 oscillation Effects 0.000 claims abstract description 50
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 28
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 27
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 27
- 238000001914 filtration Methods 0.000 claims abstract description 26
- 238000001816 cooling Methods 0.000 claims abstract description 20
- 239000000413 hydrolysate Substances 0.000 claims abstract description 13
- 239000007788 liquid Substances 0.000 claims description 35
- 238000005119 centrifugation Methods 0.000 claims description 34
- 239000007787 solid Substances 0.000 claims description 17
- 238000007865 diluting Methods 0.000 claims description 14
- 238000005485 electric heating Methods 0.000 claims description 12
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 6
- 238000004821 distillation Methods 0.000 claims description 5
- 238000007789 sealing Methods 0.000 claims description 4
- 150000005846 sugar alcohols Polymers 0.000 claims description 4
- 238000003113 dilution method Methods 0.000 claims description 2
- 238000010790 dilution Methods 0.000 abstract description 16
- 239000012895 dilution Substances 0.000 abstract description 16
- JVTAAEKCZFNVCJ-UHFFFAOYSA-M Lactate Chemical compound CC(O)C([O-])=O JVTAAEKCZFNVCJ-UHFFFAOYSA-M 0.000 abstract description 7
- 238000011084 recovery Methods 0.000 abstract description 5
- 238000005886 esterification reaction Methods 0.000 abstract description 3
- 238000010438 heat treatment Methods 0.000 description 12
- 239000000110 cooling liquid Substances 0.000 description 9
- 230000007062 hydrolysis Effects 0.000 description 9
- 238000006460 hydrolysis reaction Methods 0.000 description 9
- 239000012535 impurity Substances 0.000 description 8
- 238000005303 weighing Methods 0.000 description 8
- JJTUDXZGHPGLLC-UHFFFAOYSA-N lactide Chemical compound CC1OC(=O)C(C)OC1=O JJTUDXZGHPGLLC-UHFFFAOYSA-N 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 3
- 238000006068 polycondensation reaction Methods 0.000 description 3
- 108010009736 Protein Hydrolysates Proteins 0.000 description 2
- 239000012153 distilled water Substances 0.000 description 2
- 238000007151 ring opening polymerisation reaction Methods 0.000 description 2
- 238000007086 side reaction Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 238000012668 chain scission Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002309 gasification Methods 0.000 description 1
- -1 i.e. Chemical compound 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 230000003534 oscillatory effect Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000007363 ring formation reaction Methods 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 238000004448 titration Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/09—Preparation of carboxylic acids or their salts, halides or anhydrides from carboxylic acid esters or lactones
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/43—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation
- C07C51/44—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation by distillation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/08—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides with the hydroxy or O-metal group of organic compounds
Abstract
The invention relates to a method for recovering lactic acid in the process of polylactic acid synthesis, in particular to a method and a device for recovering lactic acid from a polylactic acid synthetic substrate, which comprises the steps of adding water to the polylactic acid synthetic substrate for dilution, and oscillating for 5-8min to obtain the synthetic substrate after oscillation and dilution; placing the diluted synthetic substrate in a centrifuge, cooling to 3-5 ℃, performing centrifugal operation, adding alcohol during the centrifugal process, and centrifuging to obtain hydrolysate; filtering and distilling the hydrolysate to obtain the lactic acid. According to the invention, alcohol is added in the recovery process of polylactic acid, so that the lactic acid-containing components in the polylactic acid synthetic substrate can be subjected to esterification reaction to generate lactate, and more lactate hydrolysate can be effectively separated in the centrifugal process by adding water to the polylactic acid synthetic substrate for dilution oscillation, so that the recovery purity of lactic acid is greatly improved.
Description
Technical Field
The invention relates to a method for recovering lactic acid in a polylactic acid synthesis process, in particular to a method and a device for recovering lactic acid from a polylactic acid synthesis substrate.
Background
Polylactic acid has been widely spotlighted as a biodegradable environment-friendly material due to its unique properties and excellent processability. Polylactic acid can be synthesized through two ways, namely, direct polycondensation of lactic acid monomers, namely a direct method; the other is ring-opening polymerization of lactide, i.e., lactide is synthesized from lactic acid and then polylactic acid is obtained through ring-opening polymerization, i.e., indirect method. At present, the latter is commonly adopted at home and abroad to synthesize polylactic acid. In actual production, raw material lactic acid is heated to remove free water in solution, then polycondensation is carried out to generate lactic acid oligomer, and the water of combination generated in polycondensation reaction is removed, so that the lactic acid oligomer is cracked to generate lactide. During the chain scission and cyclization process, a part of lactic acid oligomer with higher molecular weight is generated, and side reactions such as high-temperature oxidation and carbonization also occur. These side reaction products are generally dark brown, pungent, and viscous liquids. Through the research of the reaction mechanism of lactide synthesis by lactic acid, the residual substrate can be treated by hydrolysis. After the non-reusable components in the hydrolysate are removed, the lactide synthesis reaction can be carried out again. Therefore, how to recover high-purity lactic acid from a substrate for polylactic acid synthesis is a problem to be solved.
Disclosure of Invention
The present invention aims to solve the above-mentioned drawbacks of the prior art by providing a method and apparatus for recovering lactic acid from a substrate for polylactic acid synthesis.
The technical scheme adopted by the invention is as follows:
provided are a method and a device for recovering lactic acid from a polylactic acid synthetic substrate, comprising the following steps:
s1: diluting the polylactic acid synthetic substrate with water, and oscillating for 5-8min to obtain an oscillating and diluted synthetic substrate;
s2: placing the diluted synthetic substrate in a centrifuge, cooling to 3-5 ℃, performing centrifugal operation, adding alcohol during the centrifugal process, and centrifuging to obtain hydrolysate;
s3: filtering and distilling the hydrolysate to obtain the lactic acid.
As a preferred technical scheme of the invention: the ratio of the polylactic acid synthetic substrate to water in the dilution process is 1: 0.2-0.25.
As a preferred technical scheme of the invention: the alcohol is low-polyhydric alcohol, and the ratio of the low-polyhydric alcohol to the diluted synthetic substrate is 1: 3-3.15.
As a preferred technical scheme of the invention: the lower alcohol is methanol or ethanol.
The device for recovering the lactic acid from the polylactic acid synthetic substrate comprises an oscillation diluting device for diluting and oscillating the polylactic acid synthetic substrate, a centrifugal device for centrifuging the synthetic substrate and a filtering and distilling device for filtering and distilling hydrolysate, wherein the centrifugal device is arranged in an outer barrel and is driven by a motor to rotate and centrifuge, the filtering and distilling device is arranged on the inner wall of the outer barrel and is used for filtering and heating and distilling the hydrolysate after rotating and centrifuging, and the oscillation diluting device is arranged above the outer barrel and is driven by a vibration motor to oscillate.
As a preferred technical scheme of the invention: the centrifugal device comprises a centrifugal cylinder, the bottom of the centrifugal cylinder is a circular truncated cone-shaped structure with a small diameter at the bottom, and a part between the circular truncated cone-shaped structure at the bottom of the centrifugal cylinder and the centrifugal cylinder main body is a circle of annular centrifugal screen.
As a preferred technical scheme of the invention: the centrifugal cylinder is characterized in that a cooling cavity is arranged inside the cylinder wall of the circular truncated cone-shaped structure at the bottom of the centrifugal cylinder, a liquid exchange port communicated with the cooling cavity is arranged outside the centrifugal cylinder, and the liquid exchange port is sealed through being in threaded connection with a sealing cover.
As a preferred technical scheme of the invention: the filtering and distilling device comprises a lactic acid collecting tank positioned on the inner wall of the outer barrel, the section of the lactic acid collecting tank is of an inclined structure with a high inside and a low outside, the lactic acid collecting tank is positioned on the outer side of the bottom of the centrifugal screen, a circle of filter screen with the same size as the lactic acid collecting tank is arranged at the opening at the top of the lactic acid collecting tank, and a plurality of circles of electric heating wires are arranged on the inner bottom surface of the lactic acid collecting tank.
As a preferred technical scheme of the invention: an annular water baffle is arranged on the inner wall of the outer barrel and right above the lactic acid collecting tank, the cross section of the water baffle is of an inclined structure with a high inside and a low outside, and a water collecting tank is arranged below the water baffle.
As a preferred technical scheme of the invention: the utility model discloses a vibration diluting device, including the vibration bottle, the vibration bottle is for leaking hopper-shaped structure the bottom of vibration bottle is equipped with the liquid outlet, be equipped with on the liquid outlet and be used for control the valve of liquid outlet break-make, the vibration bottle passes through fixing device to be fixed on the urceolus, fixing device is including closely cup jointing solid fixed ring on the vibration bottle outer wall, it is equidistant a plurality of support arms that are equipped with of circumference on solid fixed ring's the outer wall, the end of support arm is equipped with the snap ring, the snap ring with the upper end joint of urceolus, vibrating motor is two at least, and the symmetry install in on solid fixed ring's the outer wall.
Compared with the prior art, the method and the device for recovering the lactic acid from the polylactic acid synthetic substrate have the following advantages: according to the invention, alcohol is added in the recovery process of polylactic acid, so that the lactic acid-containing components in the polylactic acid synthetic substrate can be subjected to esterification reaction to generate lactate, and more lactate hydrolysate can be effectively separated in the centrifugal process by adding water to the polylactic acid synthetic substrate for dilution oscillation, so that the recovery purity of lactic acid is greatly improved.
Drawings
FIG. 1 is a schematic overall structure of a preferred embodiment of the present invention;
FIG. 2 is an exploded view of the overall structure in the preferred embodiment of the present invention;
FIG. 3 is a top view of the outer barrel in the preferred embodiment of the present invention;
FIG. 4 is a cross-sectional view taken along the line A-A in FIG. 3 in accordance with a preferred embodiment of the present invention;
FIG. 5 is a schematic structural diagram of a centrifugal cylinder according to a preferred embodiment of the present invention;
FIG. 6 is a top view of a centrifuge bowl in accordance with a preferred embodiment of the present invention;
FIG. 7 is a cross-sectional view taken in the direction B-B of FIG. 6 in accordance with a preferred embodiment of the present invention;
fig. 8 is a schematic structural view of the oscillation bottle and the fixing device in the preferred embodiment of the present invention.
Illustration of the drawings: 1. an outer cylinder; 11. a lactic acid collection tank; 12. filtering with a screen; 13. a water baffle; 14. a water collection tank; 15. an electric heating wire; 2. oscillating the bottle; 21. a liquid outlet; 22. a valve; 3. a centrifugal cylinder; 31. centrifuging the screen; 32. a cooling chamber; 33. a liquid changing port; 34. a sealing cover; 4. a fixing device; 41. a fixing ring; 42. a support arm; 43. a snap ring; 44. a vibration motor; 5. a motor bracket; 6. a motor; 7. and a bearing.
Detailed Description
It should be noted that, in the case of no conflict, the embodiments and the features in the embodiments may be combined with each other, and the technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1 to 8, the preferred embodiment of the present invention provides an apparatus for recovering lactic acid from a polylactic acid synthetic substrate, comprising an oscillation diluting device for diluting the polylactic acid synthetic substrate by oscillation, a centrifuging device for centrifuging the synthetic substrate, and a filtering and distilling device for filtering and distilling a hydrolysate, wherein the centrifuging device is installed inside an outer cylinder 1 and is driven by a motor 6 to perform rotational centrifugation, the filtering and distilling device is installed on the inner wall of the outer cylinder 1 and is used for filtering and heating and distilling the hydrolysate after rotational centrifugation, and the oscillation diluting device is installed above the outer cylinder 1 and is driven by a vibration motor 44 to perform oscillation.
Oscillation diluting device includes oscillation bottle 2, oscillation bottle 2 is for leaking hopper-shaped structure, bottom at oscillation bottle 2 is equipped with liquid outlet 21, be equipped with the valve 22 that is used for controlling the break-make of liquid outlet 21 on liquid outlet 21, oscillation bottle 2 passes through fixing device 4 to be fixed on urceolus 1, fixing device 4 is including closely cup jointing solid fixed ring 41 on oscillation bottle 2 outer wall, it is equidistant a plurality of support arms 42 that are equipped with of circumference on solid fixed ring 41's the outer wall, support arm 42's end is equipped with snap ring 43, snap ring 43 and urceolus 1's upper end joint, vibrating motor 44 is two at least, and the symmetry is installed on solid fixed ring 41's outer wall. Water and the polylactic acid synthetic substrate are placed in the oscillation bottle 2, and the vibration motor 44 drives the fixing ring 41 to vibrate, so that the oscillation bottle 2 is driven to vibrate continuously to realize uniform mixing and dilution of the water and the polylactic acid synthetic substrate. The support arm 42 is made of an aluminum alloy material, has high toughness, and can shake when the vibration motor 44 vibrates, so that the fixing ring 41 and the oscillation bottle 2 are easily resonated. So that the oscillation effect is enhanced. After the oscillatory dilution is completed, valve 22 is opened and the diluted synthesis substrate is discharged from outlet 21 and falls into the interior of the underlying centrifuge.
Specifically, the centrifugal device comprises a centrifugal cylinder 3, the bottom of the centrifugal cylinder 3 is a circular truncated cone-shaped structure with a small bottom diameter, and a circle of annular centrifugal screen 31 is arranged between the circular truncated cone-shaped structure at the bottom of the centrifugal cylinder 3 and the main body of the centrifugal cylinder 3. A cooling cavity 32 is arranged inside the cylinder wall of the circular truncated cone-shaped structure at the bottom of the centrifugal cylinder 3, a liquid exchange port 33 communicated with the cooling cavity 32 is arranged outside the centrifugal cylinder 3, and the liquid exchange port 33 is sealed through being in threaded connection with a sealing cover 34. Further, motor 6 passes through motor support 5 to be installed in the inside of urceolus 1, and motor support 5 has two circular baffles and the bracing piece between the circular baffle edge to constitute, and motor 6 installs in motor support 5's inside, and motor 6's output shaft passes the circular baffle of top and with 3 coaxial fixes in bottom of centrifuge bowl, secondly, installs bearing 7 on the circular baffle of top, rotates through bearing 7 between the circular baffle of top and the centrifuge bowl 3 to be connected. During the centrifugation process, the synthetic substrate diluted in the centrifuge bowl 3 has a small outward displacement distance during the centrifugation process due to the large viscosity of the lactic acid oligomer with high molecular weight, and the hydrolysate formed by the hydrolyzed lactate and water has a small viscosity, and is outwardly displaced along with the centrifugal force and thrown out of the centrifugal screen 31. In order to prevent the lactic acid therein from forming lactide, the temperature during centrifugation is lowered by the cooling chamber 32. Specifically, cooling liquid can be added into the cooling cavity 32 through the liquid exchange port 33, so that the diluted synthetic substrate is cooled in the centrifugal process, and the lactide is prevented from being formed by the esterification reaction among lactic acid molecules.
Besides, the filtering and distilling device comprises a lactic acid collecting tank 11 positioned on the inner wall of the outer barrel 1, the cross section of the lactic acid collecting tank 11 is of an inclined structure with a high inside and a low outside, the lactic acid collecting tank 11 is positioned at the outer side of the bottom of the centrifugal screen 31, a circle of filter screen 12 with the same size is arranged at the opening at the top of the lactic acid collecting tank 11, and a plurality of circles of electric heating wires 15 are arranged on the inner bottom surface of the lactic acid collecting tank 11. An annular water baffle 13 is arranged on the inner wall of the outer barrel 1 and right above the lactic acid collecting tank 11, the cross section of the water baffle 13 is of an inclined structure with a high inside and a low outside, and a water collecting tank 14 is arranged below the water baffle 13. The lactate and the water thrown out from the centrifugal screen 31 enter the lactic acid collection tank 11, and the lactate and the water are continuously hydrolyzed to generate lactic acid. Finally, the heating wire 15 is electrified for heating, the water in the inner part is distilled, and the lactic acid is left for recovery. Wherein, the water moves upwards after distillation and gasification and touches the bottom surface of the water baffle 13 at normal temperature to form water drops, and the cross section of the water baffle 13 is in an inclined structure with a high inside and a low outside, so that the distilled water can fall into the water collecting tank 14 along with the bottom surface of the water baffle 13 to be recovered.
It is necessary to supplement that the lactic acid collecting tank 11, the water baffle 13 and the water collecting tank 14 are all fixed with the inner wall of the outer barrel 1 in a clamping manner, so that the lactic acid collecting tank can be conveniently detached to recover distilled water and lactic acid.
Example 1:
a method for recovering lactic acid from a polylactic acid synthesis substrate, comprising the steps of: weighing 10g of polylactic acid synthetic substrate and 2g of water, placing the polylactic acid synthetic substrate and the water in an oscillation bottle 2, starting a vibration motor 44, oscillating for 5min to obtain an oscillation diluted synthetic substrate, and opening a valve 22 of a liquid outlet 21; enabling the synthetic substrate after oscillation dilution to flow downwards and fall into a centrifugal cylinder 3, adding cooling liquid with the temperature of 3 ℃ into a cooling cavity 32 of the centrifugal cylinder 3, starting a motor 6 for centrifugation, adding 36g of ethanol during the centrifugation process, throwing hydrolysis liquid out of a centrifugal screen 31 to a lactic acid collecting tank 11 during the centrifugation process, filtering solid impurities through a filter screen 12, standing for 10min, starting an electric heating wire 15 for heating, and distilling water to obtain lactic acid.
Example 2:
a method for recovering lactic acid from a polylactic acid synthesis substrate, comprising the steps of: weighing 10g of polylactic acid synthetic substrate and 2g of water, placing the polylactic acid synthetic substrate and the water in an oscillation bottle 2, starting a vibration motor 44, oscillating for 8min to obtain an oscillation diluted synthetic substrate, and opening a valve 22 of a liquid outlet 21; enabling the synthetic substrate after oscillation dilution to flow downwards and fall into a centrifugal cylinder 3, adding cooling liquid with the temperature of 3 ℃ into a cooling cavity 32 of the centrifugal cylinder 3, starting a motor 6 for centrifugation, adding 36g of ethanol during the centrifugation process, throwing hydrolysis liquid out of a centrifugal screen 31 to a lactic acid collecting tank 11 during the centrifugation process, filtering solid impurities through a filter screen 12, standing for 10min, starting an electric heating wire 15 for heating, and distilling water to obtain lactic acid.
Example 3:
a method for recovering lactic acid from a polylactic acid synthesis substrate, comprising the steps of: weighing 10g of polylactic acid synthetic substrate and 2g of water, placing the polylactic acid synthetic substrate and the water in an oscillation bottle 2, starting a vibration motor 44, oscillating for 5min to obtain an oscillation diluted synthetic substrate, and opening a valve 22 of a liquid outlet 21; enabling the synthetic substrate after oscillation dilution to flow downwards and fall into a centrifugal cylinder 3, adding cooling liquid at 4 ℃ into a cooling cavity 32 of the centrifugal cylinder 3, starting a motor 6 for centrifugation, adding 36g of ethanol during the centrifugation, throwing hydrolysis liquid out of a centrifugal screen 31 to a lactic acid collecting tank 11 during the centrifugation, filtering solid impurities through a filter screen 12, standing for 10min, starting an electric heating wire 15 for heating, and distilling water to obtain lactic acid.
Example 4:
a method for recovering lactic acid from a polylactic acid synthesis substrate, comprising the steps of: weighing 10g of polylactic acid synthetic substrate and 2g of water, placing the polylactic acid synthetic substrate and the water in an oscillation bottle 2, starting a vibration motor 44, oscillating for 5min to obtain an oscillation diluted synthetic substrate, and opening a valve 22 of a liquid outlet 21; enabling the synthetic substrate after oscillation dilution to flow downwards and fall into a centrifugal cylinder 3, adding cooling liquid with the temperature of 5 ℃ into a cooling cavity 32 of the centrifugal cylinder 3, starting a motor 6 for centrifugation, adding 36g of ethanol during the centrifugation process, throwing hydrolysis liquid out of a centrifugal screen 31 to a lactic acid collecting tank 11 during the centrifugation process, filtering solid impurities through a filter screen 12, standing for 10min, starting an electric heating wire 15 for heating, and distilling water to obtain lactic acid.
Example 5:
a method for recovering lactic acid from a polylactic acid synthesis substrate, comprising the steps of: weighing 10g of polylactic acid synthetic substrate and 3g of water, placing the polylactic acid synthetic substrate and the water in an oscillation bottle 2, starting a vibration motor 44, oscillating for 5min to obtain an oscillation diluted synthetic substrate, and opening a valve 22 of a liquid outlet 21; enabling the synthetic substrate after oscillation dilution to flow downwards and fall into a centrifugal cylinder 3, adding cooling liquid with the temperature of 3 ℃ into a cooling cavity 32 of the centrifugal cylinder 3, starting a motor 6 for centrifugation, adding 39g of ethanol during the centrifugation process, throwing hydrolysis liquid out of a centrifugal screen 31 to a lactic acid collecting tank 11 during the centrifugation process, filtering solid impurities through a filter screen 12, standing for 10min, starting an electric heating wire 15 for heating, and distilling water to obtain lactic acid.
Example 6:
a method for recovering lactic acid from a polylactic acid synthesis substrate, comprising the steps of: weighing 10g of polylactic acid synthetic substrate and 2g of water, placing the polylactic acid synthetic substrate and the water in an oscillation bottle 2, starting a vibration motor 44, oscillating for 8min to obtain an oscillation diluted synthetic substrate, and opening a valve 22 of a liquid outlet 21; enabling the synthetic substrate after oscillation dilution to flow downwards and fall into a centrifugal cylinder 3, adding cooling liquid with the temperature of 3 ℃ into a cooling cavity 32 of the centrifugal cylinder 3, starting a motor 6 for centrifugation, adding 24g of ethanol during the centrifugation process, throwing hydrolysis liquid out of a centrifugal screen 31 to a lactic acid collecting tank 11 during the centrifugation process, filtering solid impurities through a filter screen 12, standing for 10min, starting an electric heating wire 15 for heating, and distilling water to obtain lactic acid.
Example 7:
a method for recovering lactic acid from a polylactic acid synthesis substrate, comprising the steps of: weighing 10g of polylactic acid synthetic substrate and 2g of water, placing the polylactic acid synthetic substrate and the water in an oscillation bottle 2, starting a vibration motor 44, oscillating for 5min to obtain an oscillation diluted synthetic substrate, and opening a valve 22 of a liquid outlet 21; enabling the synthetic substrate after oscillation dilution to flow downwards and fall into a centrifugal cylinder 3, adding cooling liquid at 4 ℃ into a cooling cavity 32 of the centrifugal cylinder 3, starting a motor 6 for centrifugation, adding 36g of glycerol during the centrifugation, throwing hydrolysis liquid out of a centrifugal screen 31 to a lactic acid collecting tank 11 during the centrifugation, filtering solid impurities through a filter screen 12, standing for 10min, starting an electric heating wire 15 for heating, and distilling water to obtain lactic acid.
Example 8:
a method for recovering lactic acid from a polylactic acid synthesis substrate, comprising the steps of: weighing 10g of polylactic acid synthetic substrate and 2g of water, placing the polylactic acid synthetic substrate and the water in an oscillation bottle 2, starting a vibration motor 44, oscillating for 5min to obtain an oscillation diluted synthetic substrate, and opening a valve 22 of a liquid outlet 21; enabling the synthetic substrate after oscillation dilution to flow downwards and fall into a centrifugal cylinder 3, adding cooling liquid with the temperature of 5 ℃ into a cooling cavity 32 of the centrifugal cylinder 3, starting a motor 6 for centrifugation, adding 36g of propanol during the centrifugation process, throwing hydrolysis liquid out of a centrifugal screen 31 to a lactic acid collecting tank 11 during the centrifugation process, filtering solid impurities through a filter screen 12, standing for 10min, starting an electric heating wire 15 for heating, and distilling water to obtain lactic acid.
Comparative example 1:
in the case of example 1, the polylactic acid synthesis substrate was directly centrifuged without adding water for dilution.
Comparative example 2:
in the case of example 1, with no other changes in conditions, no alcohol was added during centrifugation.
This example was carried out by determining the purity of the lactic acid recovered in examples 1 to 8 and comparative examples 1 to 2 by the neutralization titration method.
The results are given in the table below.
| Lactic acid purity (%) | |
| Example 1 | 96.3 |
| Example 2 | 96.5 |
| Example 3 | 96.2 |
| Example 4 | 96.3 |
| Example 5 | 92.6 |
| Example 6 | 90.3 |
| Example 7 | 88.4 |
| Example 8 | 91.5 |
| Comparative example 1 | 75.6 |
| Comparative example 2 | 51.1 |
As can be seen from the data in the above table, the purity of lactic acid was the highest when the lactic acid was recovered by the method of examples 1-4, wherein the purity of lactic acid recovered by comparative examples 1 and 2 was significantly lowered in the case of direct centrifugation without dilution with water or without addition of alcohol during centrifugation. It is demonstrated that the methods of examples 1 to 4 of the present invention are effective in improving the purity of lactic acid when recovering lactic acid.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (10)
1. A method for recovering lactic acid from a polylactic acid synthesis substrate, comprising the steps of:
s1: diluting the polylactic acid synthetic substrate with water, and oscillating for 5-8min to obtain an oscillating and diluted synthetic substrate;
s2: placing the diluted synthetic substrate in a centrifuge, cooling to 3-5 ℃, performing centrifugal operation, adding alcohol during the centrifugal process, and centrifuging to obtain hydrolysate;
s3: filtering and distilling the hydrolysate to obtain the lactic acid.
2. The method and apparatus for recovering lactic acid from a substrate for polylactic acid synthesis according to claim 1, wherein: the ratio of the polylactic acid synthetic substrate to water in the dilution process is 1: 0.2-0.25.
3. The method and apparatus of claim 1 for recovering lactic acid from a polylactic acid synthesis substrate, wherein: the alcohol is low-polyhydric alcohol, and the ratio of the low-polyhydric alcohol to the diluted synthetic substrate is 1: 3-3.15.
4. The method and apparatus for recovering lactic acid from a substrate for polylactic acid synthesis according to claim 3, wherein: the lower alcohol is methanol or ethanol.
5. An apparatus for recovering lactic acid from a substrate for polylactic acid synthesis for carrying out the method for recovering lactic acid from a substrate for polylactic acid synthesis according to any one of claims 1 to 4, wherein: including being used for diluting the vibration diluting device that the vibration was diluted to polylactic acid synthetic substrate, being used for carrying out centrifugal device and being used for filtering the distillation's filtration distillation plant to the synthetic substrate, centrifugal device installs inside urceolus (1), rotates the centrifugation through motor (6) drive, filter distillation plant and install in the inner wall of urceolus (1) for to rotate behind the centrifugation hydrolysate through filtering and heat the distillation, vibration diluting device installs in urceolus (1) top to vibrate through vibrating motor (44) drive vibration.
6. The method and apparatus for recovering lactic acid from a substrate for polylactic acid synthesis according to claim 5, wherein: the centrifugal device comprises a centrifugal cylinder (3), the bottom of the centrifugal cylinder (3) is of a circular truncated cone-shaped structure with a small diameter at the bottom, and a part between the circular truncated cone-shaped structure at the bottom of the centrifugal cylinder (3) and a centrifugal cylinder (3) main body is a circle of annular centrifugal screen (31).
7. The method and apparatus for recovering lactic acid from a substrate for polylactic acid synthesis according to claim 6, wherein: the centrifugal cylinder is characterized in that a cooling cavity (32) is arranged inside the cylinder wall of the circular truncated cone-shaped structure at the bottom of the centrifugal cylinder (3), a liquid exchange port (33) communicated with the cooling cavity (32) is arranged outside the centrifugal cylinder (3), and the liquid exchange port (33) is sealed through being in threaded connection with a sealing cover (34).
8. The method and apparatus for recovering lactic acid from a substrate for polylactic acid synthesis according to claim 6, wherein: the filtering and distilling device comprises a lactic acid collecting tank (11) located on the inner wall of the outer barrel (1), the section of the lactic acid collecting tank (11) is of an inclined structure with a high inside and a low outside, the lactic acid collecting tank (11) is located on the outer side of the bottom of the centrifugal screen (31), a circle of filter screen (12) with the same size is arranged at the opening at the top of the lactic acid collecting tank (11), and a plurality of circles of electric heating wires (15) are arranged on the inner bottom surface of the lactic acid collecting tank (11).
9. The method and apparatus for recovering lactic acid from a substrate for polylactic acid synthesis according to claim 8, wherein: an annular water baffle (13) is arranged on the inner wall of the outer barrel (1) and right above the lactic acid collecting tank (11), the cross section of the water baffle (13) is of an inclined structure with a high inside and a low outside, and a water collecting tank (14) is arranged below the water baffle (13).
10. The method and apparatus for recovering lactic acid from a substrate for polylactic acid synthesis according to claim 5, wherein: oscillation diluting device includes oscillation bottle (2), oscillation bottle (2) are for leaking hopper-shaped structure the bottom of oscillation bottle (2) is equipped with liquid outlet (21), be equipped with on liquid outlet (21) and be used for control valve (22) of liquid outlet (21) break-make, oscillation bottle (2) are fixed through fixing device (4) on urceolus (1), fixing device (4) are including closely cup jointing solid fixed ring (41) on oscillation bottle (2) outer wall, it is equidistant a plurality of support arms (42) to be the circumference on the outer wall of solid fixed ring (41), the end of support arm (42) is equipped with snap ring (43), snap ring (43) with the upper end joint of urceolus (1), vibrating motor (44) are two at least, and the symmetry install in on the outer wall of solid fixed ring (41).
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Cited By (1)
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| CN115073280A (en) * | 2022-08-02 | 2022-09-20 | 马鞍山同杰良生物材料有限公司 | Method for recovering high-optical-purity lactic acid from polylactic acid synthetic substrate |
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